net/batman-adv/bitarray.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /* Copyright (C) 2006-2018  B.A.T.M.A.N. contributors:
   3  *
   4  * Simon Wunderlich, Marek Lindner
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of version 2 of the GNU General Public
   8  * License as published by the Free Software Foundation.
   9  *
  10  * This program is distributed in the hope that it will be useful, but
  11  * WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  13  * General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program; if not, see <http://www.gnu.org/licenses/>.
  17  */
  18
  19 #include "bitarray.h"
  20 #include "main.h"
  21
  22 #include <linux/bitmap.h>
  23
  24 #include "log.h"
  25
  26 /* shift the packet array by n places. */
  27 static void batadv_bitmap_shift_left(unsigned long *seq_bits, s32 n)
  28 {
  29         if (n <= 0 || n >= BATADV_TQ_LOCAL_WINDOW_SIZE)
  30                 return;
  31
  32         bitmap_shift_left(seq_bits, seq_bits, n, BATADV_TQ_LOCAL_WINDOW_SIZE);
  33 }
  34
  35 /**
  36  * batadv_bit_get_packet() - receive and process one packet within the sequence
  37  *  number window
  38  * @priv: the bat priv with all the soft interface information
  39  * @seq_bits: pointer to the sequence number receive packet
  40  * @seq_num_diff: difference between the current/received sequence number and
  41  *  the last sequence number
  42  * @set_mark: whether this packet should be marked in seq_bits
  43  *
  44  * Return: true if the window was moved (either new or very old),
  45  *  false if the window was not moved/shifted.
  46  */
  47 bool batadv_bit_get_packet(void *priv, unsigned long *seq_bits,
  48                            s32 seq_num_diff, int set_mark)
  49 {
  50         struct batadv_priv *bat_priv = priv;
  51
  52         /* sequence number is slightly older. We already got a sequence number
  53          * higher than this one, so we just mark it.
  54          */
  55         if (seq_num_diff <= 0 && seq_num_diff > -BATADV_TQ_LOCAL_WINDOW_SIZE) {
  56                 if (set_mark)
  57                         batadv_set_bit(seq_bits, -seq_num_diff);
  58                 return false;
  59         }
  60
  61         /* sequence number is slightly newer, so we shift the window and
  62          * set the mark if required
  63          */
  64         if (seq_num_diff > 0 && seq_num_diff < BATADV_TQ_LOCAL_WINDOW_SIZE) {
  65                 batadv_bitmap_shift_left(seq_bits, seq_num_diff);
  66
  67                 if (set_mark)
  68                         batadv_set_bit(seq_bits, 0);
  69                 return true;
  70         }
  71
  72         /* sequence number is much newer, probably missed a lot of packets */
  73         if (seq_num_diff >= BATADV_TQ_LOCAL_WINDOW_SIZE &&
  74             seq_num_diff < BATADV_EXPECTED_SEQNO_RANGE) {
  75                 batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
  76                            "We missed a lot of packets (%i) !\n",
  77                            seq_num_diff - 1);
  78                 bitmap_zero(seq_bits, BATADV_TQ_LOCAL_WINDOW_SIZE);
  79                 if (set_mark)
  80                         batadv_set_bit(seq_bits, 0);
  81                 return true;
  82         }
  83
  84         /* received a much older packet. The other host either restarted
  85          * or the old packet got delayed somewhere in the network. The
  86          * packet should be dropped without calling this function if the
  87          * seqno window is protected.
  88          *
  89          * seq_num_diff <= -BATADV_TQ_LOCAL_WINDOW_SIZE
  90          * or
  91          * seq_num_diff >= BATADV_EXPECTED_SEQNO_RANGE
  92          */
  93         batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
  94                    "Other host probably restarted!\n");
  95
  96         bitmap_zero(seq_bits, BATADV_TQ_LOCAL_WINDOW_SIZE);
  97         if (set_mark)
  98                 batadv_set_bit(seq_bits, 0);
  99
 100         return true;
 101 }